Investigators tasked with sifting through phone numbers found on a cell phone bill may be perplexed to find calls or texts coming in from the 111 area code. A check of published lists of area codes shows there is no such area code. So how could there be calls listed as coming in from a non-existent area code?

Here's the answer: AT&T and other cell carriers have been using the 111 area code to indicate calls or text messages coming into a cell phone that were generated online with an instant messaging service. In other words, it's most likely an unidentified person was on a computer, sending chat messages or voice calls to the target phone using an Internet chat program that has cross-platform capabilities to cell phones.

Websites where the public reports strange or unwanted calls like 800notes.com suggests the chief culprit is Yahoo Instant Messenger and the most commonly displayed number will be 111-047-0400. Investigators should note the 111 number is not specific to the user of the instant messaging program and will not directly yield the identity of the person who was the source of the communication. Rather, it is an indicator of web to cell phone communications from an unknown party.

Robert Scott is a Los Angeles-based private investigator and creator of websites for private investigators, including SkipSmasher.com. Reprint permission.